# scipy.fftpack.dst¶

scipy.fftpack.dst(x, type=2, n=None, axis=-1, norm=None, overwrite_x=False)[source]

Return the Discrete Sine Transform of arbitrary type sequence x.

Parameters: x : array_like The input array. type : {1, 2, 3}, optional Type of the DST (see Notes). Default type is 2. n : int, optional Length of the transform. If n < x.shape[axis], x is truncated. If n > x.shape[axis], x is zero-padded. The default results in n = x.shape[axis]. axis : int, optional Axis along which the dst is computed; the default is over the last axis (i.e., axis=-1). norm : {None, ‘ortho’}, optional Normalization mode (see Notes). Default is None. overwrite_x : bool, optional If True, the contents of x can be destroyed; the default is False. dst : ndarray of reals The transformed input array.

idst
Inverse DST

Notes

For a single dimension array x.

There are theoretically 8 types of the DST for different combinations of even/odd boundary conditions and boundary off sets [R49], only the first 3 types are implemented in scipy.

Type I

There are several definitions of the DST-I; we use the following for norm=None. DST-I assumes the input is odd around n=-1 and n=N.

           N-1
y[k] = 2 * sum x[n]*sin(pi*(k+1)*(n+1)/(N+1))
n=0


Only None is supported as normalization mode for DCT-I. Note also that the DCT-I is only supported for input size > 1 The (unnormalized) DCT-I is its own inverse, up to a factor 2(N+1).

Type II

There are several definitions of the DST-II; we use the following for norm=None. DST-II assumes the input is odd around n=-1/2 and n=N-1/2; the output is odd around k=-1 and even around k=N-1

          N-1
y[k] = 2* sum x[n]*sin(pi*(k+1)*(n+0.5)/N), 0 <= k < N.
n=0


if norm='ortho', y[k] is multiplied by a scaling factor f

f = sqrt(1/(4*N)) if k == 0
f = sqrt(1/(2*N)) otherwise.


Type III

There are several definitions of the DST-III, we use the following (for norm=None). DST-III assumes the input is odd around n=-1 and even around n=N-1

                           N-2
y[k] = x[N-1]*(-1)**k + 2* sum x[n]*sin(pi*(k+0.5)*(n+1)/N), 0 <= k < N.
n=0


The (unnormalized) DCT-III is the inverse of the (unnormalized) DCT-II, up to a factor 2N. The orthonormalized DST-III is exactly the inverse of the orthonormalized DST-II.

New in version 0.11.0.

References

 [R49] (1, 2) Wikipedia, “Discrete sine transform”, http://en.wikipedia.org/wiki/Discrete_sine_transform

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